Airless hydraulic system supply

ABSTRACT

A brake fluid supply vessel with a pressurizable expansible bladder therein for expelling fluid through the bottom of the vessel. Vents communicate with the bladder and the tank around the bladder to allow exhaustion of air therefrom.

United States Patent [191 Blomgren, Sr. et al.

[ Feb. 13, 1973 AIR LESS HYDRAULIC SYSTEM SUPPLY Inventors: Oscar C.Blomgren, Sr.; Oscar C. Blomgren, Jr., both of North Chicago, Ill.

Assignee: Tuxco Corporation Filed: Feb. 19, 1971 Appl. No.: 116,839

vs. C! ..222/396, 222/530 Int. Cl. ..'B67d 5/54 Field ofSearch...222/394, 406, 407, 386.5, 396,

References Cited UNITED STATES PATENTS 2/1956 Milster et al. 222/386.52/1968 Rak ...222/386.5 X

2/1970 Bauer ..222/386.5 12/1958 Hicks ..222/386.5

Primary Examiner--Stanley H. Tollberg Attorney-Mann, Brown, McWilliams &Bradway ABSTRACT A brake fluid supply vessel with a pressurizableexpansible bladder therein for expelling fluid through the bottom of thevessel. Vents communicate with the bladder and the tank around thebladder to allow exhaustion of air therefrom.

16 Claims, 8 Drawing Figures PAIENIEUFEBIISIQYS 3.718171 SHEET 10F 3INVENTORS H62 38 OSCAR c. BLOMGREN/JR OSCAR c. BLOMGREN/SR ATTORNEYSPAIENTEU EB 191s 3.71s;171 SHEET 2 (IF 3 iNVENTORS OSCAR C. BLOMGREN JROSCAR C. BLOMGREN,SR.

, ATTORNEYS PATENTEDFEBIBIHIS 3,716,171 SHEET 30F 3 INVENTORS OSCAR C.BLOMGRENJR OSCAR C. BLOMGREN,SR

ATTORNEYS 1 AIRLESS HYDRAULIC SYSTEM SUPPLY The present invention isdirected to new and useful improvements in hydraulic brake systems fluidsupply reservoirs for charging brake systems with fluid.

In recent years, some hydraulic brake fluid dispensers have taken theform of a tank within which the hydraulic brake fluid is introducedwhile a source of compressed air is utilized to expel the fluid from thetank and into a brake system. In one form of such apparatus, a containerwas filled with brake fluid and a source of compressed air coupled tothe tank so as to expel the fluid out of the tank. In this type ofapparatus, air was in direct contact with the hydraulic fluid.Temperature changes could cause condensation of water within the tankwhich, when mixed with the brake fluid, could cause brake failure. Also,compressed air could be blown into the hydraulic brake system which isundesirable. Because of this, it was proposed to form a tank of twoparts with a flexible rubber diaphragm spanning the two parts anddividing the tank into an air chamber and an hydraulic fluid chamber.Air was then introduced into the air side of the tank to expel the fluidthrough expansion of the diaphragm against the fluid. In this type ofapparatus, the diaphragm was clamped between flanges of the two tanksections. This meant that the diaphragm was compressed in order to forma seal between the two sections. This caused excessive working and wearof the diaphragm with the result that the diaphragm could rupture andallow air to escape into the hydraulic brake system.

With the foregoing in mind, the major purposes of the present inventionare to form an air pressure operated brake fluid supply tank in such amanner'that an expansible element within the tank is protected againststresses or abrasions, to so form a unit of this class that the systemis effectively sealed against air leakage into the brake fluid, to forma unit of this class which allowsall working parts to be easily removedfrom the tank for cleaning, inspection and repair, to form a unit ofthis class with an access opening seal which becomes tightened aspressure is increased within the tank, to form a system of this class ina manner such that air leaks and water condensation within the tank aresubstantially eliminated, and to form a unit of this class so that it isrelatively simple to manufacture and use.

These and other purposes will appear from time to time in the course ofthe ensuing specification and claims when taken with the accompanyingdrawings, in which: V

FIG. 1 is a perspective view of atypical portable brake fluid reservoirembodying the present invention;

FIG. 2 is a sectional view of an outlet from the bottom of the reservoirillustrated in FIG. 1;

FIG. 3 is a sectional view of the reservoir illustrated in FIG. 1;

FIG. 4 is a sectional view similar to FIG. 3, while illustrating adifferent operative position (partly expanded bladder) of the parts fromthatshown in FIG. 3;

FIG. 5 is a sectional view similar to FIGS. 3 and 4 while illustrating afully expanded condition of the bladder of the assembly of FIGS. 3 and4; I

FIG. 6 is a plan view of certain portions of the assembly illustratedinFIGS. 3-5;

FIG.- 7 is a side view of the elements illustrated in FIG. 6, whileillustrating their relation to certain other elements in the assembly;and

FIG. 8 is a plan view of the assembly as illustrated in FIG. 1.

Like elements are designated by like characters throughout thespecification and drawings.

With particular reference now to the drawings, and in the first instanceto FIG. 1, the numeral 20 generally designates a brake fluid reservoirin the form of a general cylindrical tank having a dome-shaped top andbottom. The tank may be conveniently fabricated by making the tank inupper and lower half sections, while welding the sections at thedividing line to provide a closed vessel. The tank includes an accessopening in the top wall thereof, which is covered by a cover assemblygenerally designated at 21. The tank is preferably formed as a portableassembly. For the purposes of portability, support rods 22, 23 and 24(FIG. 8) may be spaced equidistantly around the axis of the tank andwelded to the lower portion of the tank. Each rod includes a portionextending below the bottom wall of the tank to serve as a support forthe tank. One rod, as for example, rod 22, may include an angularly bentlower portion 25 which extends toward the axis of the tank to serve as asupport stand. The other rods 23 and 24 may include lower portions 230and 24a extending at right angles to a fore and aft vertical planethrough the tank to serve as axles for transport wheels 27 and 28 (FIG.8). Rod 22 and a portion of rod 23 are seen in FIG. 3.

Each of the rods 22, 23 and 24 may include upper offset portions 29,which are spaced from the wall of the tank to define a wrap-aroundsupport area for an operating hose 30, which may be wound about the tankas shown in FIG. 1 for purposes of storage. A manipulating handle 31 maybe welded to the exterior of the tank at a point between the wheels 27and 28 to allow the tank to be tilted about the axis of the wheels toraise the stand defined by the offset 25 above the ground, whereupon theassembly may be easily wheeled to any desired location of use.

Handle 31 may have a hand grip 31a on its upper end to facilitatewheeled movement and a hand grip 31b intermediate its ends to facilitatelifting and bodily transport of the unit.

The cover assembly 21 is provided with certain valves and ports to allowthe tank to be filled with hydraulic brake fluid in a manner which willbe described. The bottom of the tank is provided with an outlet in theform of a plug of metal generally designated at 32 which is seatedwithin an opening in the bottom wall 34 of the tank and welded theretoso as to seal the opening around the plug. The plug 32 includes anupwardly convex top surface 33 and a cylindrical side surface having anannular groove 35 milled therein. Apertures 36 are drilled into the wallof the groove at spaced points about the axis of the plug to providecommunication between the interior of the tank and a axial bore 37within the plug, which affords communication through an elbow fitting 38with a shutoff valve 39 of the fluid supply hose 30. Hose 30 may includean additional shut-off valve 41 in the length thereof and terminate in anozzle fitting 42, which is formed an adapted for coupling to an inletfitting for a brakefluid supply system.

In accordance with the invention, the cover assembly 21 includes aclosure plate in the form of a generally oval plate 43, which isslightly larger than the oval access opening in the top wall of thetank. The closure plate 43 is adapted to be inserted within the accessopening and then sealed against the inner wall of the tank around theopening by means of a gasket 44 which is compressed between the coverplate 43 and the wall of the tank around the opening. Cap screws 45 arepassed through the wall of the tank around the access opening and intothe closure plate 43 so as to bring the plate 43 into a tightly sealedrelation to the upper wall ofthe tank around the access opening.

The closure plate 43 includes a brake fluid filler opening 46 therein,which is adapted to be closed and sealed by a cap 47, which is screwthreaded into the opening and which bears against a sealing gasket 48.The cap 47 includes a spring closed air inlet valve 49, which projectsabove the cap and which may be coupled to an air supply hose for thepurpose of pressurizing the interior of the tank to collapse the bladderprior to filling the tank.

The central portion of the closure plate 43 is provided with a springclosed vent valve fitting 50 having a manually operated button 51 foropening the interior of the tank to atmospheric pressure, upondepression of the button for purposes which will be described. Theclosure plate 43 also carries an air fitting generally designated at 52on the side of the closure plate opposite to the filler opening side.The fitting is formed as bosses 52a and 52b cast integrally with theplate and projecting above and below the plate. The air inlet fitting 52includes a central bore 53 extending through the bosses and plate. Thetop of the bore is closed by an air gauge (not shown). Upper boss 52ahas transverse threaded bores communicating with bore 53 and receivingan air inlet valve 54, a pressure relief valve 55 and a vent valve 56.Valve 54 is of the spring closed type. Vent valve 56 is a spring closedvalve and includes an actuating button 57 which, upon depressionthereof, opens the valve for communication of the bore 53 to theatmosphere.

Manually actuated spring closed vent valves are known to the art and forthis reason the valves 50 and 56 are not described in detail herein.Similarly, the air inlet valves 49 and 54 are of a type known to theart, such as air inlet valves for automotive tires and for this reasonthey are not described in detail herein.

Pressure relief valve 55 is set to open when a preselected maximumbladder pressure is exceeded. In further accordance with'the invention,connection 58 couples a bladder 59 to the boss 52b. Bladder 59 is amolded rubber construction which, in the unexpanded condition thereof,has a generally inverted cup-shaped form as is seen in FIG. 3. In theunexpanded condition, the bladder consists of an outer wall 59a definedby the upper part of the bladder and an inner wall 59b which consists ofthe lower portion of the bladder, which is folded upwardly within theupper portion 590 to define the cup-shaped form. Bladder 59 is formedfrom a flexible material and preferably a fabricated material comprisedof an inner nylon plastic sheet with an outer coating of Buena N rubber.Bladder 59 is adapted to be expanded form the position illustrated inFIG. 3 by pressurizing the interior thereof through the air fitting 54so that it moves from the condition illustrated in FIG. 3 to a partiallyexpanded condition, which is generally represented in FIG. 4 and a fullyexpanded condition as illustrated in FIG. 5, wherein the bladder mayfill approximately to percent of the volume of the tank's interior.

In further accordance with the invention, the lower portion of theclosure plate 43 is provided with posts 60 which are spaced around thecircumference thereof and project downwardly a short distance past theboss 52b. The posts 60 receive the ends of the screws 45. An elastomericprotective disc 61 is fitted around the fitting 58 between boss 52b andthe bladder 59. The disc 61 has a diameter such as to extend beyond theoutline of the cover plate to prevent the bladder from moving upwardlyagainst any part of the closure plate, and thus protect the bladdermember from abrasions and possible rupture. The disc 61 includes anannular marginal taped edge 62, which may flex upwardly in response to apressurized condition of the bladder for purposes of forming a circularclosure around the plate 43 and against the inner wall of the tank. Disc61 may be provided with small apertures to allow equalization ofpressure on opposite sides of the disc. For example, four 3/16 inchholes may be formed through the disc and spaced equidistantly aroundconnection 58.

In operation the bladder fills approximately 80 percent to 90 percent ofthe volume of the tank when it is fully expanded. At the end of a brakefilling operation, the remainder of the volume of the tank containsbrake fluid. The tank volume may be approximately 5 gallons in a typicalembodiment of the invention.

To recharge the unit, the vent valve 56 of the bladder air fitting isactuated to release air from the bladder. At the same time, the ventvalve 50 for the fluid side of the tank is opened so that the fluid sideof the tank is open to atmospheric pressure also. This collapses thebladder 59. To insure complete collapse of the bladder, an air hose iscoupled to the air inlet valve 59 of the filler cap and the vent valve56 of the bladder air inlet fitting is opened to cause the bladder toassume the inverted cup-shaped form as appears in FIG. 3. The tank isthen ready to be recharged with hydraulic brake fluid. The filler cap 47is then removed and a charge of brake fluid approximating the volume ofthe tank is introduced through the filler cap opening. At this time someair remains within the tank. The filler cap is then replaced and sealedtightly in the filler opening. An air hose for the bladder inlet valve54 is then used to partially pressurize the bladder. At the same timethe vent valve 50 for the hydraulic side of the tank is opened and keptopen so that any air remaining within the tank may be exhausted throughthe opening of this valve. When air has been completely exhausted fromthe interior of the tank, brake fluid will flow from the vent valveopening at which time the vent valve 50 may be closed. The tank is thenready for another brake system charging cycle. The air valve 54 for thebladder may then be closed, if desired.

At this time, the bladder may be expanded approximately 20 percent sothat the total volume in the tank consists of the partially expandedbladder and a volume of brake fluid filling the remainder of theinterior of the tank.

When it is desired to charge a brake system, the hose 30 is coupled tothe brake system supply line and the air inlet valve 54 coupled to anair hose so as to again subject the bladder to air pressure and cause itto fully expand. As the bladder expands, it expels the hydraulic brakefluid through the outlet plug 32 in the bottom of the tank. When thebladder is fully expanded, the bottom of the bladder forms a seal aroundthe outlet opening by contacting the fluid on the lower wall of the tankaround the outlet opening and pressing it against the wall.

As the bladder approaches its fully expanded condition, it forces theedge of protective disc 61 upwardly. The outer annular edge 62 of thedisc may be forced upwardly into a contacting relation with the upperwall of the tank around the closure plate 43.

When the bladder is fully expanded and the substantial part of the brakefluid within the tank is supplied through the hose to a brake system orsystems being recharged, valve 39 in the fluid supply line may beclosed, whereupon the bladder may be collapsed in the manner previouslymentioned and the tank refilled.

It should be understood that the system may be utilized for dischargingsubstantially all of the brake fluid within the tank in one operation,or may be utilized for discharging small amounts of brake fluid at atime until the bladder is completely expanded and the substantial partofthe brake fluid discharged from the tank.

The expansible bladder is protected against abrasives and unnecessarywear. As formed, the assembly minimizes the possibility of air in thebrake system. The seal around the access opening becomes tighter as thepressure in the tank increases. The pressure force from the air in theinterior of the bladder is equalized by the pressure forces from thefluid exterior to the bladder. The cover assembly is so formed that it,together with the bladder and disc, are easily removed from the tank forservice and cleaning.

1 claim: I g

l. A hydraulic system supply vessel for supplying air free hydraulicfluid to a hydraulic system, including a tank adapted to contain asupply of hydraulic fluid, said tank having an outlet opening formed ina bottom wall thereof, said opening including a fitting adapted to becoupled to a hydraulic fluid supply line, said tank having an accessopening in the top wall thereof with a closure fitted within the Openingand sealed to the wall of said tank around said opening, an air inletfitting formed in said closure and an expansible hollow bladder carriedby said closure within said tank and coupled to said air inlet fitting,the interior of said bladder being in communication solely with said airinlet fitting, said closure having a normallyclosed filler openingtherein for filling said tank with hydraulic fluid, said air inletadapted to be coupled to a source of air pressure whereby air may expandsaid bladder against a volume of fluid within said tank and force fluidout of said outlet opening, and a flexible disc of elastomeric materialformed aroundsaid air inlet fitting above said bladder and underlyingsaid closure, said disc having an area greater than the area of saidclosure.

2. The structure of claim 1 wherein said bladder has a generallyinverted cup shaped form in the unexpanded condition thereof and has asize such as to be expanded into a generally cylindrical form of avolume comprising a substantial portion of the volume of said tank.

3. The structure of claim 1 wherein said filler opening includes aclosure cap therefor, said cap having an air inlet fitting for thepurpose of pressurizing the interior of the tank with air in the absenceof fluid to force said bladder into its unexpanded, inverted, cupshapedform.

4. The structure of claim 1 wherein said closure includes a manuallyactuated valve to allow release of air and fluid through said closurewhen said tank is filled with fluid.

5. The structure of claim 1 wherein said air inlet fitting has a boretherein and said closure carries a pressure relief valve, a normallyclosed, manually actuated vent valve and a normally closed air inletvalve communicating with said bore at a location exterior to said tank.

6. The structure of claim 1 wherein said closure is defined by a plateadapted to be received within an access opening of matchingconfiguration in the top wall of the tank, the area of said plate beinglarger than the area of said access opening and being shaped so that thesaid plate may be received through said access opening with the marginalarea thereof underlying the marginal-area of said tank around saidaccess opening, and sealing means between said marginal areas.

7. The structure of claim 1 wherein said outlet opening in said tank isformed through an upwardly convex element positioned above the lowerwall of said tank, said element having a central bore communicating withsaid fitting, said element having a reduced portion underlying saidupwardly concave part, said reduced portion having passage means thereinand communicating with said bore to allow flow of fluid from said tankand through said bore into said fitting.

8. The structure of claim 7 wherein said bladder is adapted uponexpansion thereof to move against said upwardly concave part andtherearound.

9. A liquid supply vessel for supplying air free liquid through a supplyhose, including a tank adapted to contain a supply of liquid, said tankhaving an outlet opening formed in a bottom wall thereof, said openingincluding a fitting adapted to be coupled to a liquid supply hose, saidtank including means for developing pressure therein against a volume ofliquid therein for expelling liquid through said opening, said tankhaving a plurality of support rods spaced around said tank and fixed tothe wall thereof, the major portion of the length of each rod extendinggenerally vertically, the

uppermost portions of each rod being offset outwardly from the wall ofsaid tank to define a hose receiving storage area between the wall ofthe tank and said portions, the lower ends of a pair of said rods beingextended laterally outwardly from said tank in alignment with oneanother, and support wheels rotatably carried on said lower laterallyextended portions of said pair of rods.

10 The structure of claim 9 wherein a rod other than said pair includesa laterally offset portion serving as a stand.

11. A hydraulic system supply vessel for supplying air free fluid to anhydraulic system, including a tank adapted to contain a supply ofhydraulic fluid, said tank having an outlet opening formed in the bottomwall thereof, said opening including a fitting adapted to be coupled toa hydraulic fluid supply line, said tank having an air fitting and afiller fitting in the wall thereof,

an expansible hollow air bladder within said tank and coupled to saidair fitting, the interior of said bladder being in communication solelywith said air inlet fitting, said filler fitting including a normallyclosed air inlet valve to provide a pressurized condition in the fluidvolume of said tank around said bladder, said tank including a normallyclosed and manually operated vent valve communicating with the fluidvolume of said tank around said bladder, said air inlet fittingincluding a normally closed and manually actuated vent valve adapted tocommunicate the interior of said bladder to the atmosphere, said airinlet fitting including a normally closed air inlet valve providing ameans for pressurizing the interior of said bladder.

12. The structure of claim 11 wherein said air inlet fitting includes apressure relief valve for limiting the maximum pressure within saidbladder.

13. The structure of claim 11 wherein said bladder, fittings and valvesare carried by a closure plate removably sealed across an access openingto said tank.

14. A liquid supply vessel for supplying air free liquid to a supplyline, including a tank adapted to contain a liquid, said tank having anoutlet opening formed in the bottom wall thereof, said opening includinga fitting adapted to be coupled to a liquid supply line, said tankhaving an air fitting and a filler fitting in the wall thereof, anexpansible hollow air bladder within said tank and coupled to said airfitting, the interior of said bladder being in communication solely withsaid air inlet fitting, said filler fitting including a normally closedair inlet valve to provide a pressurized condition in the fluid volumeof said tank around said bladder, said tank including a normally closedand manually operated vent valve communicating with the fluid volume ofsaid tank around said bladder, said air inlet fitting including anormally closed and manually actuated vent valve adapted to communicatethe interior of said bladder to the atmosphere, said air inlet fittingalso including a normally closed air inlet valve providing a means forpressurizing the interior of said bladder.

15. The structure of claim 14 wherein said air inlet fitting includes apressure relief valve for limiting the maximum pressure within saidbladder.

16. The structure of claim 14 wherein said bladder, fittings and valvesare carried by a closure plate removably sealed across an access openingin said tank.

1. A hydraulic system supply vessel for supplying air free hydraulicfluid to a hydraulic system, including a tank adapted to contain asupply of hydraulic fluid, said tank having an outlet opening formed ina bottom wall thereof, said opening including a fitting adapted to becoupled to a hydraulic fluid supply line, said tank having an accessopening in the top wall thereof with a closure fitted within the openingand sealed to the wall of said tank around said opening, an air inletfitting formed in said closure and an expansible hollow bladder carriedby said closure within said tank and coupled to said air inlet fitting,the interior of said bladder being in communication solely with said airinlet fitting, said closure having a normally closed filler openingtherein for filling said tank with hydraulic fluid, said air inletadapted to be coupled to a source of air pressure whereby air may expandsaid bladder against a volume of fluid within said tank and force fluidout of said outlet opening, and a flexible disc of elastomeric materialformed around said air inlet fitting above said bladder and underlyingsaid closure, said disc having an area greater than the area of saidclosure.
 1. A hydraulic system supply vessel for supplying air freehydraulic fluid to a hydraulic system, including a tank adapted tocontain a supply of hydraulic fluid, said tank having an outlet openingformed in a bottom wall thereof, said opening including a fittingadapted to be coupled to a hydraulic fluid supply line, said tank havingan access opening in the top wall thereof with a closure fitted withinthe opening and sealed to the wall of said tank around said opening, anair inlet fitting formed in said closure and an expansible hollowbladder carried by said closure within said tank and coupled to said airinlet fitting, the interior of said bladder being in communicationsolely with said air inlet fitting, said closure having a normallyclosed filler opening therein for filling said tank with hydraulicfluid, said air inlet adapted to be coupled to a source of air pressurewhereby air may expand said bladder against a volume of fluid withinsaid tank and force fluid out of said outlet opening, and a flexibledisc of elastomeric material formed around said air inlet fitting abovesaid bladder and underlying said closure, said disc having an areagreater than the area of said closure.
 2. The structure of claim 1wherein said bladder has a generally inverted cup-shaped form in theunexpanded condition thereof and has a size such as to be expanded intoa generally cylindrical form of a volume comprising a substantialportion of the volume of said tank.
 3. The structure of claim 1 whereinsaid filler opening includes a closure cap therefor, said cap having anair inlet fitting for the purpose of pressurizing the interior of thetank with air in the absence of fluid to force said bladder into itsunexpanded, inverted, cup-shaped form.
 4. The structure of claim 1wherein said closure includes a manually actuated valve to allow releaseof air and fluid through said closure when said tank is filled withfluid.
 5. The structure of claim 1 wherein said air inlet fitting has abore therein and said closure carries a pressure relief valve, anormally closed, manually actuated vent valve and a normally closed airinlet valve communicating with said bore at a location exterior to saidtank.
 6. The structure of claim 1 wherein said closure is defined by aplate adapted to be received within an access opening of matchingconfiguration in the top wall of the tank, the area of said plate beinglarger than the area of said access opening and being shaped so that thesaid plate may be received through said access opening with the marginalarea thereof underlying the marginal area of said tank around saidaccess opening, and sealing means between said marginal areas.
 7. Thestructure of claim 1 wherein said outlet opening in said tank is formedthrough an upwardly convex element positioned above the lower wall ofsaid tank, said element having a central bore communicating with saidfitting, said element having a reduced portion underlying said upwardlyconcave part, said reduced portion having passage means therein andcommunicating with said bore to allow flow of fluid from said tank andthrough said bore into said fitting.
 8. The structure of claim 7 whereinsaid bladder is adapted upon expansion thereof to move against saidupwardly concave part and therearound.
 9. A liquid supply vessel forsupplying air free liquid through a supply hose, including a tankadapted to contain a supply of liquid, said tank having an outletopening formed in a bottom wall thereof, said opening including afitting adapted to be coupled to a liquid supply hose, said tankincluding means for developing pressure therein against a volume ofliquid therein for expelling liquid through said opening, said tankhaving a plurality of support rods spaced around said tank and fixed tothe wall thereof, the major portion of the length of each rod extendinggenerally vertically, the uppermost portions of each rod being offsetoutwardly from the wall of said tank to define a hose receiving storagearea between the wall of the tank and said portions, the lower ends of apair of said rods being extended laterally outwardly from said tank inalignment with one another, and support wheels rotatably carried on saidlower laterally extended portions of said pair of rods. 10 The structureof claim 9 wherein a rod other than said pair includes a laterallyoffset portion serving as a stand.
 11. A hydraulic system supply vesselfor supplying air free fluid to an hydraulic system, including a tankadapted to contain a supply of hydraulic fluid, said tank having anoutlet opening formed in the bottom wall thereof, said opening includinga fitting adapted to be coupled to a hydraulic fluid supply line, saidtank having an air fitting and a filler fitting in the wall thereof, anexpansible hollow air bladder within said tank and coupled to said airfitting, the interior of said bladder being in communication solely withsaid air inlet fitting, said filler fitting including a normally closedair inlet valve to provide a pressurized condition in the fluid volumeof said tank around said bladder, said tank including a normally closedand manually operated vent valve communicating with the fluid volume ofsaid tank around said bladder, said air inlet fitting including anormally closed and manually actuated vent valve adapted to communicatethe interior of said bladder to the atmosphere, said air inlet fittingincluding a normally closed air inlet valve providing a means forpressurizing the interior of said bladder.
 12. The structure of claim 11wherein said air inlet fitting includes a pressure relief valve forlimiting the maximum pressure within said bladder.
 13. The structure ofclaim 11 wherein said bladder, fittings and valves are carried by aclosure plate removably sealed across an access opening to said tank.14. A liquid supply vessel for supplying air free liquid to a supplyline, including a tank adapted to contain a liquid, said tank having anoutlet opening formed in the bottom wall thereof, said opening includinga fitting adapted to be coupled to a liquid supply line, said tankhaving an air fitting and a filler fitting in the wall thereof, anexpansible hollow air bladder within said tank and coupled to said airfitting, the interior of said bladder being in communication solely withsaid air inlet fitting, said filler fitting including a normally closedair inlet valve to provide a pressurized condition in the fluid volumeof said tank around said bladder, said tank including a normally closedand manually operated vent valve communicating with the fluid volume ofsaid tank around said bladder, said air inlet fitting including anormally closed and manually actuated vent valve adapted to communicatethe interior of said bladder to the atmosphere, said air inlet fittingalso including a normally closed air inlet valve providing a means forpressurizing the interior of said bladder.
 15. The structure of claim 14wherein said air inlet fitting includes a pressure relief valve forlimiting the maximum pressure within said bladder.